Fuse integrity indicator



Jm 935- F. (2. LA MAR 1,989,482

FUSE INTEGRITY INDIC'ATOR Filed Sept. 2, 1932 6 l 36' .7/ I w Z3 5 -ZZ30mmvsm'om.

Patented Jan." 29, 1935 UNITED STATES PATENT OFFICE I I l 1 FUSE mrsc immmcsroa I v M 0. LI Mar, New York, N. Y.

"91 M011 September I, 1 32, Serial N0. 831,438

' 8 Cum]. ((1 200-421) This invention relates to electricity,particularly to electrical conduits and housings, and more especially todevices known as distribution and fuse cabinets. g

It is well known that, at the present time, it is largely the custom tooriginate a plurality of electric circuits at one distributing point.These circuits at the point of origin are protected by thermal fuses. Inorder to promote the safety of those who have occasion to work aboutsuch distribution cabinets or panels, it is the custom in many cases, toso construct the distribution panels that they are what are known as"dead front", that is, normally no conducting parts .carrying currentare so exposed that a person may accidentally touch them.

The parts exposed toview are, panels of insulating material carryingupon their rear face the fuse structure which is inserted in a circuit.When it is desired to ascertain whether or not a fuse is intact it isnecessary to remove both the insulating froht facing or panel and thefuse itself. when the fuse is removed it is only by the use ofsupplementary apparatus that one is enabled to determine whether or notthe fuse is intact. This is exceedingly troublesome, and so troublesomethat the average householder is quite unable to apply proper tests todetermine the integrity of a fuse under such conditions.

Attempts have been made to overcome the difficulty by providing smallorifices in the insulating face or panel in which the pointed end of aconductor including a lamp may be inserted which thereby comes incontact with portions of the electrical circuit of opposite polarity,but

this method has proved rather unsatisfactory.

A principal object of applicant's invention is to provide a constructionof dead front electric circuit distribution box which will be such thatthe integrity of a fuse hidden behind the dead front may be ascertainedeven without removing the dead front.

In describing the invention in detail and the particular embodimentsselected to illustrate the invention reference is had to theaccompanying drawing and the several views thereon in which likecharacters of reference designate like parts throughout the severalviews and in which:

Figure 1 is a front elevational view of a panel box with a portion ofthe cover removed to more clearly show the internal construction; Fig. 2is a cross-sectional view of the device as shown in Fig. i, on the planeindicated by the line II-lI of Fig. I, viewed in the direction of thearrows at the ends of the line; Fig. 3 is a cross sectional view of thedevice, "as shown by Fig. 2, upon the plane indicated by the lineIII-.411, viewed in the direction of the arrows at the ends of the line;Fig. 4 is a view from. the rear of a I dead front blade.

The distributing box of applicant's invention preferably includes ametallic box frame 1 having a rear wall 2, side walls 3 and 4: top andbottom walls, only one of which, the bottom wall 5, is shown, and afront wall designated as a whole by 6. The front wall is formed in twoparts,- a part 7 hinged at 8 which covers the entire front of the boxbut which is apertured to receive a door 8 hinged as at 9. By thisconstruction the hinged front may be swung on. the hinge 8 so as toexpose the entire inside of the box to facilitate work therein while forthe ordinary insertion or replacement of a fuse the supplementary door8, only, would 'be moved upon swing-hinges as 9.

Within the box, bus bars as 10, 11 and 12 are suitably positioned andinsulatingly supported from contact with the metal of the box.

Forwardly of the bus bars an insulating frame work, designated as a.whole by 13, is mounted. This frame work is-supported from the back orrear 2 of the distribution box by the projections, as 14 and i5,fastening to a mounting plate 16 Ivghioh is in turn attached to the rearface of the x. If it is desired to make connections to one of the busbars a metallic double pronged member 17 is attached to a bus bar. as11, by any suitable means, as by screw 18, and another two prongedmember, as 19, is positioned on the insulating frame 13 a properdistance from member 17, that is, a distance about the length of a fuseto be used. The connection to double pronged member 19 for the circuitis made by a conductor as 21. a

In order to inserta fuse between members 1'! and 19 a metallic member 22is mounted on the rear of an insulating panel 23. This metallic membercarries two clips 24 and 25 positioned to engage with the two prongs 28and 27 of the metallic member 17 connected to the bus bar 11. Inaddition the metallic member 22 carries a clip 28 adapted to receive theknife blade 29 of a knife blade fuse. Of course it is to be understoodthat the showing of clip 28 for the reception of a knife blade fuse isnot intended to excludethe use of a clip suitable for receiving the endof a ferrule type fuse. I

In order to connect with the double pronged m mber 19 a metallic member29' is positioned on the rear of the insulating panel 23. This member29' is constructed exactly like the member 22, in that it affords clipsfor receiving the two prongs of member 19, and also a clip for receivinga knife blade corresponding to the knife blade 29 of the fuse 20.

From the above description itfwill be seen that a fuse; as 20, may beinserted in the clips attached to the rear of an insulating panel, as23, and then that panel together with the fuse may be positioned, asshown in Fig. 3, with the clips on its rear face engaging at one end theprongs of the metallic member connected to a bus bar, and at the otherend the prongs of a metallic member connected to a conductor and therebythe fuse will be connected in circuit between the conductor and the busbar so that when the panel 23, or dead front, is in place all of theparts carrying current are covered and out of the way of accidentalcontact with a person.

The construction hereinbefore described may be duplicated as many timesas is necessary to provide the necessary number of fuses in branchcircuits and the panels, as 23, when in place will form a continuouscovering, so that no parts carrying current are exposed.

All of the parts hereinbefore described are old and well known.

Heretofore panels as 23 have been provided with orifices, one over eachof the metallic members 22 so that a small pointed conductor may beinserted therein so as to come in contact with the metallic member 22.If two conductors were so placed in proper orifices and a lamp isconnected therebetween one could learn whether or not the bus bars areactive, that is, are impressed with a difference of potential, but sucha manipulation is beyond the skill of the average householder.Furthermore, such operation would not give indication as to theintegrity of the fuse.

In order to indicate the integrity of the fuse 20 and obviate thenecessity of removing the panel carrying the fuse in order to ascertainthe condition of the fuse, applicant has provided a lamp 30. This lamp,which is preferably of the low potential, two electrode, discharge typefilled with an inert gas, such as neon, is positioned with one endresting in a cavity 31 of the insulating panel 23. This cavity connectswith an orifice 32 which is visible from the outside of the panel. Asuitable holder 33 is fastened to the panel to hold the lamp securely inplace. One terminal of the lamp is connected by a conductor 34 with themetallic member 22. The other terminal of the lamp is connected by aconductor 35, having a resistance 36, preferably of the grid leak type,inserted therein, to the metallic member 29'.

The lamp 31, as described, is connected across, or in shunt of the fuse.Normally the lamp is not lighted due to the relative resistance of thelamp and its circuit and that of the thermal element of the fuse, butwhen the fuse is destroyed, as by an excessive flow of current, thensufficient current passes through the lamp to light it. One

opening the door 8' of the case and looking at the orifice 32 willimmediately detect that orifice in which a light appears showing thatalamp is burning. Under such conditions all that is necessary to be doneis to remove the panel, take out the old fuse and replace it with a newone and then replace the panel as it was.

The detection of a blown fuse by applicant's device is merely thedetection of a lighted lamp, so that it may be done by anybody.Furthermore, no accessory apparatus whatsoever is needed.

Although I have particularly described one particular physicalembodiment of my invention and explained the principle, construction andmode of operation thereof, nevertheless, I desire to have it understoodthat the form selected is merely illustrative but does not exhaust thepossible physical embodiments of the idea of means underlying myinvention.

What I claim as new and desire to secure by Letters Patent of the UnitedStates, is:

1. In a distribution box for electric circuits of the dead front typeincluding an insulating panel upon which a fuse is mounted betweencircuit clips, the combination of a lamp mounted on the rear face ofsaid panel, being positioned back of an orifice in the panel, andconnected between the circuit clips and normally unlighted but adaptedupon the destruction of the fuse to be lighted and will then beobservable through said orifice from the outside of the panel, saidinsulating panel being readily removable from said box, thereby removingsaid fuse and lamp from theelectrical circuits, for convenientinspection, adjustment and replacement.

2. In a distribution box for electric circuits of the dead front typeincluding an insulating panel upon which a fuse is mounted betweencircuit climps, the combination of a low potential two electrode, neonfilled, discharge type lamp mounted on said panel and connected inseries-with a resistance between the said clips and positioned back ofan orifice in the insulating panel, said lamp becoming luminous onlyupon the failure of the fuse, whereby the integrity of the fuse may beascertained without disturbing the panel, said insulating panel beingreadily removable from said box, thereby removing said fuse and lampfrom the electrical circuits, for convenient inspection, adjustment andreplacement.

3. In a distribution box for electric circuits of

